Mitt Romney kept up his anti-Donald Trump crusade with an appearance on “Jimmy Kimmel Live” on Tuesday.

Romney renewed his calls for Trump to release his tax returns. He went on to say that since Trump had previously said he would release the returns but is now backing away, that he must have something to hide.

“When it comes to Donald Trump, there’s some of us who think he’s not the real deal, that he’s a phony. And there are others who think he is, so hey, prove it to us. Let us see the tax returns.”

Kimmel also had Romney read mean tweets from Trump himself as well as several Trump supporters. Among them was a man who said he wanted to go back in time to the day he once met Romney so he could punch him in the throat.